Methods :-
Rain water may be collected and recharged into the ground water aquifers through the following methods - roof top harvesting and harvesting rain water from open spaces. Roof top harvesting has been practised since ages. Even today it is practised in many places throughout the world. As we know the rain water collected from the terrace is free from any bacteriological contamination except small amount of dust and other silt particles which can be filtered. It can be diverted to the existing wells/ borewells which are in use.
In the open well method all the rain water falling on the terrace of the building is collected through pipe lines and diverted into an existing open well through a filter tank/chamber. The filter chamber helps to filter fine dust, silt and other small floating particles such as leaves which are normally found on the terrace.
The size of the filter chamber depends on the amount of rain water flows from the terrace. The bottom of the chamber is filled with broken bricks followed by gravels and coarse river sand on the top. The location of the chamber is preferred based on the site conditions either below or above ground level.As in the case of open wells, the rain water from the terrace may be diverted to a bore well also . In this case it is to be kept in mind that during excess rain fall, the rate of recharge may not match the rate of rainfall. In such situations, a percolation pit has to be provided nearby to divert the excess flow of rain water. Defunct bore wells which are not in use may also be converted in to a recharge well.
Various kinds of recharge structures are possible which can ensure that rain water percolates in the ground instead of draining away from the surface. While some structures promote the percolation of water through soil strata at shallow depth (e.g. percolation/recharge pits, recharge trench, etc) others conduct water to depths from where it joins the ground water (e.g. percolation pit with bore trench with bores/recharge well etc.)
